Hermetic compressor

ABSTRACT

A hermetic compressor includes a hermetic container, a compression element accommodated in the hermetic container, and a motor element driving the compression element. The hermetic container has an inner space therein arranged to store lubrication oil. The compression element includes a shaft unit rotating about a rotation axis. The shaft unit has an oil-feeding passage provided therein. The oil-feeding passage extends upward from a lower end of the shaft unit. The shaft unit has an oil-spattering hole provided therein. The oil-spattering hole extends substantially perpendicularly to the rotation axis. The oil-spattering hole has a first open end communicating with the oil-feeding passage and a second open end opening in the inner space of the hermetic container. The second open end has a cross-sectional area smaller than a cross-sectional area of the first open end. This hermetic compressor supplies lubrication oil to sliding component, such as a piston, of the compression element, thus operating reliably and efficiently.

TECHNICAL FIELD

The present invention relates to a hermetic compressor used for a refrigeration cycle of a refrigerator, such as a freezer.

BACKGROUND ART

Hermetic compressors used for refrigeration devices, such as of refrigerators, have recently demanded to operate efficiently for low power consumption, to generate low noise, and to have a high reliability.

FIG. 7 is a vertical sectional view of conventional hermetic compressor 5001 disclosed in Japanese Patent Laid-Open Publication No.2000-145637. FIG. 8 is a sectional view of an essential part of hermetic compressor 5001. Hermetic container 1 accommodates therein motor element 4 including stator 2 and rotor 3, and compression element 5 driven by motor element 4. Hermetic container 1 stores lubrication oil 6. Shaft 10 includes main shaft 11 having rotor 3 fixed thereto and eccentric shaft 12 arranged eccentrically to main shaft 11. Cylinder block 14 has compression chamber 15 having a substantially cylindrical shape and main bearing 20. Slot 21 is provided by cutting an upper wall of cylinder block 14. Piston 23 is inserted in compression chamber 15 of cylinder block 14 so as to be reciprocally slidable. Piston 23 is coupled to eccentric shaft 12 via connecting member 24 and piston pin 25.

Oil-feeding passage 30 is provided in shaft 10. Helical groove 32 is formed along a periphery of main shaft 11. A lower end of helical groove 32 communicates with a portion of oil-feeding passage 30 around an upper end of oil-feeding passage 30. Helical groove 32 is formed helically along the periphery of main shaft 11 from the lower end thereof toward an upper end thereof and inclines in a direction opposite to a rotation direction of shaft 10. The upper end of helical groove 32 communicates with a portion of oil-feeding passage 33 around a lower end of oil-feeding passage 33. Oil-spattering hole 40 communicates with oil-feeding passage 33 provided in eccentric shaft 12 and an outer surface of eccentric shaft 12. Oil-spattering hole 40 is directed in a substantially horizontal direction at the same height as slot 21. Oil cone 41 is fixed to a lower end of main shaft 11. One end of oil cone 41 opens in lubrication oil 6, and the other end of oil cone 41 communicates with oil-feeding passage 30.

An operation of hermetic compressor 5001 will be described below.

Rotor 3 of motor element 4 rotates shaft 10. A rotation of eccentric shaft 12 is transmitted to piston 23 via connecting member 24. Piston 23 accordingly moves reciprocally in compression chamber 15. As piston 23 reciprocally moves, refrigerant gas is supplied from a refrigeration system to compression chamber 15. After being compressed in the chamber, the refrigerant gas returns back to the refrigeration system.

The rotation of shaft 10 causes oil cone 41 to function as a pump. Lubrication oil 6 in a bottom of hermetic container 1 is pumped up through oil-feeding passage 30 by a pumping action of oil cone 41. Lubrication oil 6 is pumped up to an upper portion of oil-feeding passage 30, and is introduced to helical groove 32. Helical groove 32 inclines in the direction opposite to the rotation direction of shaft 10, i.e., in a direction in which an inertial force is applied, and generates a force pushing lubrication oil 6 upward. Lubrication oil 6 is pushed upward along helical groove 32, and is supplied to a sliding portion of shaft 10. Lubrication oil 6 reaches the upper end of helical groove 32, and then, is introduced into oil-feeding passage 33 provided in eccentric shaft 12. A part of lubrication oil 6 introduced into passage 33 is circumferentially spattered from oil-spattering hole 40 by a centrifugal force in a horizontal direction. The rest of the lubrication oil is spattered from an upper end of eccentric shaft 12. Lubrication oil 6 spattered from oil-spattering hole 40 reaches slot 21 and lubricates piston 23 and piston pin 25. Thus, lubrication oil 6 is supplied sufficiently to sliding components of hermetic compressor 5001.

In conventional hermetic compressor 5001, in the case that the compressor is driven at slow rotation or in the case that oil-spattering hole 40 has a relatively large inner diameter, a pressure produced by the centrifugal force may be applied insufficiently to lubrication oil 6 in oil-spattering hole 40. Lubrication oil 6 flies accordingly downward, not horizontally, or the oil may be spattered in other directions due to its viscosity. In this case, lubrication oil 6 does not reach slot 21 stably, thus being supplied insufficiently to the sliding components of piston 23.

SUMMARY OF THE INVENTION

A hermetic compressor includes a hermetic container, a compression element accommodated in the hermetic container, and a motor element driving the compression element. The hermetic container has an inner space therein arranged to store lubrication oil. The compression element includes a shaft unit rotating about a rotation axis. The shaft unit has an oil-feeding passage provided therein. The oil-feeding passage extends upward from a lower end of the shaft unit. The shaft unit has an oil-spattering hole provided therein. The oil-spattering hole extends substantially perpendicularly to the rotation axis. The oil-spattering hole has a first open end communicating with the oil-feeding passage and a second open end opening in the inner space of the hermetic container. The second open end has a cross-sectional area smaller than a cross-sectional area of the first open end.

This hermetic compressor supplies lubrication oil to sliding component, such as a piston, of the compression element, thus operating reliably and efficiently.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical sectional view of a hermetic compressor in accordance with an exemplary embodiment of the present invention.

FIG. 2 is a sectional view of an essential part of the hermetic compressor in accordance with the embodiment.

FIG. 3 is a sectional view of an essential part of the hermetic compressor in accordance with the embodiment.

FIG. 4 is a sectional view of an essential part of another hermetic compressor in accordance with the embodiment.

FIG. 5 is a sectional view of an essential part of still another hermetic compressor in accordance with the embodiment.

FIG. 6 is a sectional view of an essential part of a further hermetic compressor in accordance with the embodiment.

FIG. 7 is a vertical sectional view of a conventional hermetic compressor.

FIG. 8 is a sectional view of an essential part of the conventional hermetic compressor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is a vertical sectional view of hermetic compressor 1001 in accordance with an exemplary embodiment of the present invention. FIGS. 2 and 3 are sectional views of essential parts of hermetic compressor 1001.

Inner space 101A of hermetic container 101 accommodates therein motor element 104 including stator 102 and rotor 103, and compression element 105 driven by motor element 104. Inner space 101A of hermetic container 101 is arranged to store lubrication oil 106 therein. Shaft 110 includes main shaft 111, eccentric shaft 112, and sub shaft 113. Rotor 103 is fixed to main shaft 111. Eccentric shaft 112 is positioned above main shaft 111 and is arranged eccentrically to main shaft 111. Sub shaft 113 is positioned above eccentric shaft 112 and rotates about rotation axis 201A as well as main shaft 111. Balancing weight 142 is fixed to an upper portion of sub shaft 113 of shaft 110 to avoid unbalanced rotation. Shaft unit 201 includes shaft 110, balancing weight 142 assembled to shaft 110, and oil cone 141, and rotates about rotation axis 201A.

Cylinder block 114 includes compression chamber 115 having a substantially cylindrical shape, main bearing 120 supporting main shaft 111, and sub bearing 121 supporting sub shaft 113. Oil fence 122 protrudes from cylinder block 114 and above compression chamber 115. Slot 123 is formed by cutting an upper wall of compression chamber 115. Piston 126 is inserted in compression chamber 115 of cylinder block 114, and is slidable reciprocally. Piston 126 is coupled to eccentric shaft 112 via connecting member 127 and piston pin 128.

Oil-feeding passage 130 is provided in a lower portion of shaft 110. Helical groove 132 is formed along a periphery of main shaft 111. Lower end 132B of helical groove 132 communicates with upper end 130A of oil-feeding passage 130. Helical groove 132 helically extends upward from lower end 132B along the periphery of main shaft 111, and inclines in a direction opposite to a rotation direction of shaft 110. Upper end 132A of helical groove 132 communicates with lower end 133B of oil-feeding passage 133. Oil-feeding passage 130 extends through eccentric shaft 112 and sub shaft 113, and opens at opening 113C provided in upper end 113A of sub shaft 113.

Oil cone 141 is fixed to lower end 111B of main shaft 111. Lower end 141B of oil cone 141 opens in lubrication oil 106. Upper end 141A of oil cone 141 communicates with lower end 130B oil-feeding passage 130. The rotation of shaft 110 allows oil cone 141 to function as a pump. Balancing weight 142 is fixed to the upper portion of sub shaft 113 of shaft 110 to avoid unbalanced rotation. Lower end 141B of oil cone 141 provides the lower end of shaft unit 201.

Oil-spattering hole 150 is formed in sub shaft 113 and balancing weight 142 provided at the upper portion of shaft 110, and extends in a substantially horizontal direction from oil-feeding passage 133. Oil-spattering hole 150 has portions 150A and 150B extending in the substantially horizontal direction. Portion 150A is formed in sub shaft 113 of shaft 110. Portion 150B is formed in balancing weight 142. Oil-spattering hole 150 extends substantially perpendicularly to rotation axis 201A of shaft unit 201, that is, portions 150A and 150B extend substantially perpendicularly to rotation axis 201A. Each of portions 150A and 150B has a constant inner diameter and a constant cross-sectional area. Open end 1150A of portion 150A of oil-spattering hole 150 communicates with oil-feeding passage 133. Open end 2150A of portion 150A communicates with open end 1150B of portion 150B. Portion 150A of oil-spattering hole 150 is connected to open end 1150A. Portion 150B of hole 150 is connected to open end 2150B. Open end 1150B of portion 150B of oil-spattering hole 150 is connected to open end 2150A of portion 150A. Open end 2150B of portion 150B of oil-spattering hole 150 extending in balancing weight 142 opens in inner space 101A of hermetic container 101. Oil-spattering hole 150 extends substantially perpendicularly to rotation axis 201A of main shaft 111 so that open end 2150B opens in the inner space of hermetic container 101. Open end 2150B of oil-spattering hole 150 opens substantially at the same height as oil fence 122. Oil-spattering hole 150 extends in the substantially horizontal direction.

Open end 2150B of oil-spattering hole 150 has a cross-sectional area smaller than that of open end 1150A of hole 150. The cross-sectional area of oil-spattering hole 150 becomes smaller as the cross-sectional area is located away radially from rotation axis 201A of main shaft 111. That is, oil-spattering hole 150 is tapered from open end 1150A toward open end 2150B. Portion 150A formed in sub shaft 113 and providing oil-spattering hole 150 has an inner diameter not smaller than 1.5 times the inner diameter of portion 150B formed in balancing weight 142. The length of portion 150b of oil-spattering hole 150 is more than twice the inner diameter of portion 150B. Specifically, portion 150A of oil-spattering hole 150 in sub shaft 113 has a inner diameter of 3 mm and a length of 2 mm. Portion 150B in balancing weight 142 has an inner diameter of 1.5 mm and a length of 4 mm. The cross-sectional area of portion 150B is one-fourth the cross-sectional area of portion 150A.

Refrigerant used for hermetic compressor 1001 is hydrocarbon-based refrigerant, natural refrigerant, such as R134a or R600a, having ozone depletion potential of zero and a small global warming potential. The above refrigerant and lubrication oil 106 are dissolvable in each other.

An operation of hermetic compressor 1001 will be described below.

Rotor 103 of motor element 104 rotates shaft 110. The rotation of eccentric shaft 112 is transmitted to piston 126 via connecting member 127, and causes piston 126 to move reciprocally in compression chamber 115. This movement causes refrigerant gas to be sucked from a refrigeration system into compression chamber 115. After being compressed in the chamber, the refrigerant gas returns back to the refrigeration system.

Oil cone 141 functioning as a pump raises lubrication oil 106 in a bottom of hermetic container 101 up through oil-feeding passage 130. Lubrication oil 106 reaching upper end 130A of oil-feeding passage 130 is introduced to helical groove 132. Since helical groove 132 inclines in the direction opposite to the rotation direction of shaft 110, i.e., in a direction in which an inertial force is applied, helical groove 132 generates a force for pushing lubrication oil 106 upward.

Lubrication oil 106 is pushed upward along helical groove 132, and is supplied to a sliding portion of shaft 110. After reaching upper end 132A of helical groove 132, lubrication oil 106 is introduced to oil-feeding passage 133 provided in eccentric shaft 112 and sub shaft 113. A portion of lubrication oil 106 introduced into passage 133 is spattered circumferentially in horizontal directions from oil-spattering hole 150 by a centrifugal force. The rest of the lubrication oil is spattered from opening 133C of upper end 113A of sub shaft 113. The portion of lubrication oil 106 spattered from oil-spattering hole 150 reaches oil fence 122 and lubricates piston 126 and piston pin 128 via slot 123. Oil cone 141, oil-feeding passage 130, helical groove 132, and oil-feeding passage 133 provide an oil-feeding passage formed in shaft unit 201.

Next, an action of lubrication oil 106 around oil-spattering hole 150 will be described below.

Lubrication oil 106 flown into portion 150A of oil-spattering hole 150 receives a pressure outwardly produced with the centrifugal force produced by the rotation of shaft 110, so that the oil flows in the oil-spattering hole outward away from rotation axis 201A. Lubrication oil 106 receiving this pressure flows from portion 150A to portion 150B. The cross-sectional area of portion 150B is one-fourth that of portion 150A. An energy of the pressure applied to the lubrication oil is converted into an energy of speed which increases the flow speed of lubrication oil 106.

Then, lubrication oil 106 is spattered hard in horizontal directions from open end 2250B of oil-spattering hole 150 (portion 150B) provided in balancing weight 142, thus being spattered stably in a long distance. The lubrication oil is accordingly supplied to sliding components reliably, such as piston 126, thus providing hermetic compressor 1001 with high reliability. Further, the compressor has a large sealing property and has a high volumetric efficiency improved. The improvement of the efficiency appears particularly to an inverter operating in a low-speed rotation which has a large leakage loss.

According to the embodiment, portion 150B of oil-spattering hole 150 has a length about 2.7 times longer than the inner diameter of portion 150B. Portion 150B has the length greater than the inner diameter of the portion, and fixes the flow of the lubrication oil when the oil passes through portion 150B. Hence, lubrication oil 106 flies out stably from open end 2150B of oil-spattering hole 150. Portion 150B has the smallest inner diameter in the portions forming oil-spattering hole 150. If portion 150B has a length less than twice the inner diameter of the portion, lubrication oil 106 flies downward considerably in the low-speed rotation, particularly in rotation less than 30 Hz, accordingly being spattered in a short distance.

Portion 150A provided in sub shaft 113 has the largest inner diameter of the portions of oil-spattering hole 150. According to the embodiment, the inner diameter of portion 150A provided in sub shaft 113 is about twice larger than that of portion 150B provided in balancing weight 142. Thus, the inner diameter (cross-sectional area) of oil-spattering hole 150 changes a lot, a large amount of energy of the pressure applied to lubrication oil 106 in oil-spattering hole 150 is converted into the energy of speed. The lubrication oil is accordingly spattered in stable directions from oil-spattering hole 150.

If the maximum inner diameter of oil-spattering hole 150 is not greater than 1.5 times the minimum inner diameter of hole 150, that is, if the inner diameter of portion 150A of oil-spattering hole 150 is not greater than 1.5 times that of portion 150B, lubrication oil 106 flies downwardly from open end 2150B of oil-spattering hole 150. Respective centers of portions 150A and 150B may not be aligned to each other completely when balancing weight 142 is press-fitted or shrinkage-fitted to sub shaft 113. In this case, if the maximum inner diameter of oil-spattering hole 150 being not greater than 1.5 times the minimum inner diameter of hole 150, lubrication oil 106 flies considerably downwardly flies in low-speed rotation operations, particularly in a low rotation less than 30 Hz, thus flying in a short distance.

The lubrication oil may be spattered in an upward direction or a downward direction due to a particular positional relationship between the centers of portion 150A and portion 150B. However, as long as portion 150B provided in balancing weight 142 completely communicates with portion 150A provided in sub shaft 113, the lubrication oil flies horizontally stably even when the centers of portions 150A and 150B are not aligned to each other completely.

According to the embodiment, oil-spattering hole 150 has the large maximum inner diameter which is about 2 times larger than the minimum inner diameter of the hole. Hence, even if balancing weight 142 is fixed with a slight deviation, portion 150B communicates with portion 150A completely, hence allowing balancing weight 142 to be fixed to sub shaft 113 with high productivity.

Portions 150A and 150B having the cross-sectional areas different from each other are formed in sub shaft 113 and balancing weight 142, respectively, before balancing weight 142 is assembled to sub shaft 113. Balancing weight 142 is assembled to sub shaft 113 so that portion 150A completely communicates with portion 150B as to form oil-spattering hole 150, thus forming oil-spattering hole 150 easily with high productivity. This structure does not require an additional member for forming oil-spattering hole 150 having plural different cross-sectional areas, and does not require to make sub shaft 113 long for forming oil-spattering hole 150 therein, thereby reducing the height of hermetic compressor 1001.

In hermetic compressor 1001 of the embodiment, oil-spattering hole 150 consistently supplies the lubrication oil to piston 126 even in low-rotating operations, such as a rotation speed of 18 r/s.

According to the embodiment, the lubrication oil spattered from oil-spattering hole 150 reaches oil fence 122. The height or direction of oil-spattering hole 150 may be adjusted to cause the lubrication oil to reach other positions.

Oil-spattering hole 40 of hermetic compressor 5001 shown in FIGS. 7 and 8 may have the same shape as oil-spattering hole 150, thus providing the same effects. In this case, a balancing weight may be fixed to eccentric shaft 12.

FIG. 4 is a cross-sectional view of another oil-spattering hole 250 of hermetic compressor 1001 according to the embodiment. In FIG. 4, the same components as those of hermetic compressor 1001 shown in FIGS. 1 and 2 are denoted by the same reference numerals, and their description are omitted. Shaft unit 210 including sub shaft 113 and balancing weight 142 has oil-spattering hole 250 formed therein, instead of oil-spattering hole 150 shown in FIG. 2. Oil-spattering hole 250 has open ends 1250 and 2250. Open end 1250 opens in oil-feeding passage 133, and open end 2250 opens in inner space 101A of hermetic container 101. Open end 2250 has an inner diameter (a cross-sectional area) smaller than that of open end 1250. The cross-sectional area of oil-spattering hole 250 decreases monotonically and continuously in a direction away from rotation axis 201A. That is, oil-spattering hole 250 is tapered continuously from open end 1250 to open end 2250, thus having a truncated cone shape. Oil-spattering hole 250 provides the same effects as those of oil-spattering hole 150 shown in FIG. 2.

FIG. 5 is a cross-sectional view of still another oil-spattering hole 350 of hermetic compressor 1001 according to the embodiment. In FIG. 5, the same components as those of hermetic compressor 1001 shown in FIGS. 1 and 2 are denoted by the same reference numerals, and their description are omitted. Oil-spattering hole 150 shown in FIG. 2 have two portions 150A and 150B provided in two members, sub shaft 113 and balancing weight 142 of shaft unit 201, respectively. An oil-spattering hole according to the embodiment may have portions which are provided in more than two members, respectively. As shown in FIG. 4, balancing weight 142 includes inner member 142A provided around sub shaft 113, and outer member 142B provided outside of inner member 142A. Oil-spattering hole 350 has portions 350A, 350B, and 350C which are provided in three members, i.e., sub shaft 113, inner member 142A, and outer member 142B, respectively. Portions 350A, 350B, and 350C have respective constant cross-sectional areas (inner diameters). In oil-spattering hole 350, portion 350B has the cross-sectional area (inner diameter) smaller than that of portion 350A, and portion 350C has the cross-sectional area (inner diameter) smaller than that of portion 350B. Oil-spattering hole 350 has open ends 1350A and 2350C. Open end 1350A opens in oil-feeding passage 133, and open end 2350C opens in inner space 101A of hermetic container 101. Open end 2350C has an inner diameter (a cross-sectional area) smaller than that of open end 1350A. The oil-spattering hole according to the embodiment which is provided in more than two members provides the same effects as those of oil-spattering hole 150 shown in FIG. 2.

FIG. 6 is a cross-sectional view of further oil-spattering hole 450 of hermetic compressor 1001 according to the embodiment. In FIG. 6, the same components as those of hermetic compressor 1001 shown in FIGS. 1 and 2 are denoted by the same reference numerals, and their description are omitted. Oil-spattering hole 450 has portion 450A provided in sub shaft 113 and portion 450B provided in balancing weight 142. Portion 450A of oil-spattering hole 450 has open end 1450A opening in oil-feeding passage 133 and open end 2450A connected to portion 450B. Portion 450A has a constant cross-sectional area (inner diameter) from open end 1450A to open end 2450A, thus having a cylindrical shape. Portion 450B of oil-spattering hole 450 has open end 1450B connected to portion 450A and open end 2450B opening in inner space 101A of hermetic container 101. The cross-sectional area of portion 450B decreases monotonically and continuously from open end 1450B to open end 2450B. That is, portion 450B is tapered continuously from open end 1450B to open end 2450B, thus having a truncated cone shape. Open end 2450B has an inner diameter (a cross-sectional area) smaller than that of open end 1450A. Open end 1450B of portion 450B has an inner diameter (a cross-sectional area) smaller than that of open end 2450A of portion 450A connected to open end 1450B. Oil-spattering hole 450 thus including portion 450A having the cylindrical shape and portion 450B having the truncated cone shape provides the same effects as those of oil-spattering hole 150 shown in FIG. 2.

Thus, the oil spattering hole according to the embodiment has a first open end which opens in oil-feeding passage 133 and a second open end which opens in inner space 101A of hermetic container 101. The second end has a cross-sectional area (inner diameter) than that of the first open end. The oil-spattering hole provides the same effects as those of oil-spattering hole 150 shown in FIG. 2 even if the hole includes portions having various shapes.

This exemplary embodiment does not limit the scope of the present invention.

INDUSTRIAL APPLICABILITY

This hermetic compressor supplies lubrication oil to sliding component, such as a piston, of the compression element, thus operating reliably and efficiently, hence being useful for an air conditioner and a refrigerator, such as a freezer.

REFERENCE NUMERALS

101 Hermetic Container

101A Inner Space

106 Lubrication Oil

111 Shaft

120 Bearing

133 Oil-Feeding Passage

150 Oil-Spattering Hole

150A Portion of Oil-Spattering Hole

150B Portion of Oil-Spattering Hole

142 Balancing Weight

201 Shaft Unit

201A Rotation Axis

1001 Hermetic Compressor

1150A Open End of Oil-Spattering Hole

2150B Open End of Oil-Spattering Hole 

1. A hermetic compressor comprising: a hermetic container having an inner space therein, the inner space being arranged to store lubrication oil therein; a compression element accommodated in the hermetic container, the compression element including a shaft unit rotating about a rotation axis, the shaft unit including a main shaft and an eccentric shaft, and a bearing supporting the main shaft of the shaft unit; and a motor element accommodated in the hermetic container, the motor element driving the compression element, wherein the shaft unit has an oil-feeding passage provided therein, the oil-feeding passage extending upward from a lower end of the shaft unit, the shaft unit has an oil-spattering hole provided therein, the oil-spattering hole extending substantially perpendicularly to the rotation axis, the oil-spattering hole has a first open end communicating with the oil-feeding passage and a second open end opening in the inner space of the hermetic container, and the second open end has a cross-sectional area smaller than a cross-sectional area of the first open end.
 2. The hermetic compressor of claim 1, wherein the oil-spattering hole has a first portion connected to the first open end and a second portion connected to the second open end, the second portion having a cross-sectional area smaller than a cross-sectional area of the first portion.
 3. The hermetic compressor of claim 2, wherein the second portion of the oil-spattering hole is connected to the first portion of the oil-spattering hole.
 4. The hermetic compressor of claim 2, wherein the first portion and the second portion of the oil-spattering hole comprise holes having inner diameters different from each other, respectively.
 5. The hermetic compressor of claim 2, wherein the shaft unit includes a first member having the first portion of the oil-spattering hole provided therein, and a second member having the second portion of the oil-spattering hole provided therein, the second member being assembled to the first member.
 6. The hermetic compressor of claim 5, wherein the shaft unit further includes a shaft having the first portion of the oil-spattering hole provided therein, and a balancing weight having the second portion of the oil-spattering hole provided therein, the balancing weight being fixed to the shaft.
 7. The hermetic compressor of claim 2, wherein the second portion of the oil-spattering hole has a length not smaller than twice an inner diameter of the second open end.
 8. The hermetic compressor of claim 2, wherein the first open end of the oil-spattering hole has an inner diameter not smaller than 1.5 times an inner diameter of the second open end of the oil-spattering hole.
 9. The hermetic compressor of claim 1, wherein the compression element further includes a cylinder block having a compression chamber therein, a piston moving reciprocally in the compression chamber, and a connecting member for coupling the piston to the eccentric shaft of the shaft unit. 